Currently, standardization on technologies for efficiently operating a communication system by separating a traffic forwarding function and a control function of a switch apparatus is going on in an Open Networking Foundation (ONF), an Internet Engineering Task Force (IETF), a European Telecommunications Standards Institute (ETSI) ISG Network Function Virtualization (NFV), and an International Telecommunications Union Telecommunication (ITU-T).
Software-defined networking (SDN) means a user-oriented network in which a user has control authority regardless of a basic network device such as a router or a switch, etc. and a separate software controller controls a flow of traffic.
OpenFlow is one variety of SDN technology and defines an interface connecting a hardware such as a router and a controller operating in a network operating system (OS), and is a protocol for separating a control plane for controlling how to transmit a data packet through a network from a physical network and interacting with a data plane for data transmission.
An extensibility working group in the ONF is leading a drafting task on an OpenFlow specification (OF 1.x), which is a proposal of recommendation for a SDN core standard. The OpenFlow standards define connection manners and message protocols between a switch and a controller in a section of OpenFlow channel, and specify that a Transport. Layer Security (TLS) can be basically used for maintaining TCP connections, mutual authentication, and encryption.
Also, the OpenFlow standards recommend the use of ‘OPF_ECHO_REQUEST’ messages and ‘OFP_ECHO_REPLY’ messages for identifying liveness of a connection between a switch and a controller.
However, if flow entries transferred from a controller to switches are not applied simultaneously, services for them cannot be applied in a lump. Also, if even one flow entry among a plurality of flow entries needed for service application is not successfully transferred, a problem may occur in the service application.